Kepler spacecraft will detect small planets close to the size of earth.

Humanity has wondered about the heavens above since before recorded history. Recently, the discovery of hundred of planets in other star systems has sparked extraordinary interest in determining the odds of extraterrestrial life.

The Kepler mission will seek to explain one part of the puzzle by observing the brightness of over 100,000 stars over the next forty-two months. In doing so, it will be able to track earth-sized planets, generating future targets of interest for more advanced future space observatories like the Terrestrial Planet Finder and the Laser Interferometer Space Antenna.

Nearly all of the extrasolar planets detected thus far are giant planets the size of Jupiter or larger. Kepler will look for planets 30 to 600 times less massive, closer to the size of Earth and more likely to support life.

All planets in stable orbits transit across their star during their own unique annual cycle. This causes a dip in the star's apparent magnitude for an observer in the same plane. By timing these transits, the orbit and length of year can be calculated. The orbit of a planet can be used to determine if it lies within the "zone of life", where it is close enough to the sun to support liquid water, yet far enough that potential life is not destroyed by it.

"Kepler's mission is to determine whether Earth-size planets in the habitable zone of other stars are frequent or rare; whether life in our Milky Way galaxy is likely to be frequent or rare", said William Borucki, NASA's Principal Investigator on the Kepler Mission.

While Kepler will only focus on a small area of the sky, its results will be enough to enable accurate estimates of the number of earth-sized planets in our galaxy.

Kepler will use an array of 42 CCD (charge-coupled device) cameras, each measuring 50x25 mm. With a resolution of 1024x2200 each, Kepler has a total resolution of approximately 95 megapixels.

CCD cameras are used in most digital cameras and optical scanners. They are also used in astronomy and in night-vision devices due to their sensitivity to the ultraviolet and infrared ranges of light.

Mission operations will be conducted by NASA's Ames Research Center in Moffett Field, California, and are included as part of the $600 million total mission cost. Ames will contact the Kepler spacecraft twice a week using the X-band for command updates as well as system status updates. Scientific data is only downloaded once a month using the Ka-band, at a data rate of up to 4.33 Mb/s. To conserve bandwidth, Kepler will conduct partial analysis on board and only transmit data of interest to researchers.

The Kepler spacecraft will be launched at 2250 Eastern Standard Time from Cape Canaveral Air Force Station in Florida. It will use the Delta II multi-stage rocket, which has flown 140 missions while achieving a success rate of almost 99 percent.

Instead of a typical earth orbit, it will launch Kepler into an earth trailing orbit in order to block light from the sun and the moon. This orbit also avoids gravitational perturbations inherent in an Earth orbit, thus allowing for additional platform stability.

The Kepler Mission is named for Johannes Kepler, best known for his Laws of Planetary Motion.

Updated 3/8/2009

The Kepler spacecraft was launched successfully aboard a Delta II rocket in the D2925-10L launch configuration from pad 17B at 22:49:57 EST on Friday March 6th. The three-stage launch vehicle had nine additional solid rocket boosters, six for the first stage and three for the second stage. The third stage boosted the Kepler payload to its heliocentric orbit trailing Earth. Two months of testing and systems verification will occur for the next two months before Kepler begins its inspiring mission.

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